Water quality and hard water areas: what your supplier can tell you

Most questions about tap water come down to one of three things: it leaves scale everywhere, it tastes or smells odd, or it has come out a strange colour. This guide is about understanding your supply and knowing what to ask your water company. For cleaning off scale, see our limescale guide. For treating hard water at home, see water softeners.

Who looks after the quality of your water

In England and Wales:

• Your water company supplies the water and is responsible for its quality up to your property.
• The Drinking Water Inspectorate (DWI) regulates drinking water quality and checks water companies.
• CCW, the Consumer Council for Water, handles consumer complaints that the water company has not resolved.

Scotland and Northern Ireland have their own arrangements. Scottish Water and NI Water are the suppliers, with their own regulators.

Inside the boundary, the pipes and fittings are the owner's. Some problems, such as a metallic taste from old pipes or discoloured water at one tap only, come from your own plumbing rather than the supply.

What "hard water" means

The DWI's page on water hardness explains that "Water hardness is caused by dissolved calcium and magnesium." Water picks these minerals up as it passes through rock such as chalk and limestone, so hardness depends on where your water comes from. Our water softeners guide reproduces DWI's hardness bands.

A few points that are useful to know:

• Hardness is not a safety standard. DWI notes that the UK regulations "do not specify standards for hardness, calcium or magnesium".
• It can vary within an area. Your water may come from more than one source, and the mix can change through the year.
• The everyday effects are scale in kettles, showers and hot water systems, marks on taps and glass, and soap that does not lather well.

We do not make health claims either way about hard or soft water. If you have a medical reason to think about what is in your water, ask your water company for the figures and talk to your GP.

How to find your area's hardness

DWI's page links to a map of typical hardness in England and Wales, but it says that for an accurate figure you should "ask your water company directly because there are areas with local variation".

Ways to find out:

1. Your water company's website. Most have a postcode checker for hardness and a water quality report for your supply zone.
2. Ask the company. Phone or email and ask for the hardness and the water quality summary for your postcode.
3. Your bill. It names your water company if you are not sure who supplies you.

Appliance makers often ask for a hardness setting, for example on a dishwasher or a softener. Their manuals usually explain which units they use. Your water company's figure will tell you which setting to pick.

Taste and smell

DWI's page on taste and odour suggests checking whether the problem is at other taps in the house and at the neighbours' before going further. Then "contact your water company", which DWI says can "carry out investigations if necessary". DWI also says the company "will be able to help you find out if there is anything wrong with your household plumbing".

Things people commonly notice, and what they often point to:

• Only at one tap, or only the hot tap. Often something in your own plumbing: the hot water system, a tap, or a hose on an appliance.
• Only first thing in the morning. Water standing in the pipes overnight. In an older house, ask about the pipe material too; see our lead water pipes guide.
• A chlorine taste. Water companies use disinfection, and some people notice it more than others.

If you ever think fuel or a chemical may be getting into the water, DWI says to "contact your water company and local authority immediately". Do not drink it while you wait.

Discoloured water

DWI's page on discoloured water says common causes include "a burst or fracture on a water main or pump" and the condition of old cast iron mains. It says you "should not assume that it is safe to drink until you have sought advice from your water company".

What DWI suggests:

• "contact your water company immediately";
• keep a sample in a clean sealed bottle, and note the date and time;
• note each time it happens.

If only your property is affected, DWI says "you are advised to contact a qualified plumber". Discolouration at the hot taps only often points to the hot water system rather than the supply.

If the company does not sort it out

DWI says that if the company's explanation is unsatisfactory or the problem continues, you can contact CCW, and "CCWater may ask the Inspectorate to investigate your complaint". CCW's website has its complaint routes and contact numbers.

Keep a record from the start: dates, what you saw, who you spoke to and any reference numbers. It makes any complaint much easier.

What to ask your water company

A short checklist for a call or email:

• What is the hardness of the water at my postcode, and in what units?
• Can I see the water quality report for my supply zone?
• Is there any work, burst or flushing in my area that could explain what I am seeing?
• Can you test the water at my kitchen tap?
• Does your record show what the pipe from the main to my boundary is made of?

Is hard water safe to drink?

UK regulations do not set a standard for hardness. If you have a specific health concern, ask your water company for figures and speak to your GP.

Why is my tap water brown or cloudy?

Brown or orange water often follows disturbance in old iron mains, such as a burst. Cloudy or white water that clears from the bottom up in a glass is often tiny air bubbles, but ask your water company if it does not clear. For discolouration, DWI advises contacting your water company straight away and not assuming it is safe to drink.

How do I find out how hard my water is?

Use your water company's postcode checker or ask the company directly. DWI says this is more accurate than a general map.